What defined these forty nations? Based on the census data, Robbin identified thirty-four factors that he determined accounted for 87 percent of the variation across the United States. These did include race, income, and the like, but not acting alone. Rather, such markers tended to aggregate and follow the same pattern in similar places. Robbin programmed his computers to profile tens of thousands of new zip codes, sorting the results into these clusters of like-minded areas, each of which he assigned an evocative name, like the “Bohemian Mix,” “Shotguns & Pickups,” or “Young Suburbia.”

Tim Wu, The Attention Merchants, loc. 606